diff --git a/.github/workflows/ci.yaml b/.github/workflows/ci.yaml
new file mode 100644
index 0000000..3636711
--- /dev/null
+++ b/.github/workflows/ci.yaml
@@ -0,0 +1,34 @@
+name: ci
+
+on:
+  pull_request:
+  push:
+    branches:
+      - refactor_tests
+
+env:
+  API_KEY: ${{ secrets.ApiKey }}
+
+concurrency:
+  # Cancels pending runs when a PR gets updated.
+  group: ${{ github.head_ref || github.run_id }}-${{ github.actor }}
+  cancel-in-progress: true
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        python-version: ["3.9", "3.10", "3.11"]
+    steps:
+      - uses: actions/checkout@v4
+      - name: Set up Python ${{ matrix.python-version }}
+        uses: actions/setup-python@v5
+        with:
+          python-version: ${{ matrix.python-version }}
+      - name: Install dependencies
+        run: |
+          python -m pip install --upgrade pip
+          python -m pip install -r requirements_dev.txt
+      - name: Run pytest
+        run: pytest
diff --git a/requirements_dev.txt b/requirements_dev.txt
new file mode 100644
index 0000000..449fb2c
--- /dev/null
+++ b/requirements_dev.txt
@@ -0,0 +1,3 @@
+-r requirements.txt
+pytest>=7.1.2
+python-dotenv>=0.20.0
\ No newline at end of file
diff --git a/tests/__init__.py b/tests/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/tests/test_pandas.py b/tests/test_pandas.py
new file mode 100644
index 0000000..239ad4b
--- /dev/null
+++ b/tests/test_pandas.py
@@ -0,0 +1,160 @@
+from itertools import product
+import os
+
+from dotenv import load_dotenv
+from entsoe import EntsoePandasClient
+import pandas as pd
+import pytest
+
+load_dotenv()
+
+API_KEY = os.getenv("API_KEY")
+
+
+@pytest.fixture
+def client():
+    yield EntsoePandasClient(api_key=API_KEY)
+
+
+@pytest.fixture
+def start():
+    return pd.Timestamp("20171201", tz="Europe/Brussels")
+
+
+@pytest.fixture
+def end():
+    return pd.Timestamp("20180101", tz="Europe/Brussels")
+
+
+@pytest.fixture
+def country_code():
+    return "BE"  # Belgium
+
+
+@pytest.fixture
+def country_code_from():
+    return "FR"  # France
+
+
+@pytest.fixture
+def country_code_to():
+    return "DE_LU"  # Germany-Luxembourg
+
+
+STARTS = [pd.Timestamp("20171201", tz="Europe/Brussels")]
+ENDS = [pd.Timestamp("20180101", tz="Europe/Brussels")]
+COUNTRY_CODES = ["BE"]  # Belgium
+COUNTRY_CODES_FROM = ["FR"]  # France
+COUNTRY_CODES_TO = ["DE_LU"]  # Germany-Luxembourg
+
+BASIC_QUERIES_SERIES = [
+    "query_day_ahead_prices",
+    "query_net_position",
+    "query_aggregate_water_reservoirs_and_hydro_storage",
+]
+
+BASIC_QUERIES_DATAFRAME = [
+    "query_load",
+    "query_load_forecast",
+    "query_wind_and_solar_forecast",
+    "query_generation_forecast",
+    "query_generation",
+    "query_generation_per_plant",
+    "query_installed_generation_capacity",
+    "query_installed_generation_capacity_per_unit",
+    "query_imbalance_prices",
+    "query_withdrawn_unavailability_of_generation_units",
+    "query_unavailability_of_generation_units",
+    "query_unavailability_of_production_units",
+    "query_import",
+    "query_generation_import",
+]
+
+CROSSBORDER_QUERIES = [
+    "query_crossborder_flows",
+    "query_scheduled_exchanges",
+    "query_net_transfer_capacity_dayahead",
+    "query_net_transfer_capacity_weekahead",
+    "query_net_transfer_capacity_monthahead",
+    "query_net_transfer_capacity_yearahead",
+    "query_intraday_offered_capacity",
+]
+
+# pandas.Series
+
+@pytest.mark.parametrize(
+    "country_code, start, end, query",
+    product(COUNTRY_CODES, STARTS, ENDS, BASIC_QUERIES_SERIES),
+)
+def test_basic_queries_series(client, query, country_code, start, end):
+    result = getattr(client, query)(country_code, start=start, end=end)
+    assert not result.empty
+
+
+@pytest.mark.parametrize(
+    "country_code_from, country_code_to, start, end, query",
+    product(COUNTRY_CODES_FROM, COUNTRY_CODES_TO, STARTS, ENDS, CROSSBORDER_QUERIES),
+)
+def test_crossborder_queries(
+    client, query, country_code_from, country_code_to, start, end
+):
+    result = getattr(client, query)(country_code_from, country_code_to, start=start, end=end)
+    assert not result.empty
+
+
+def test_query_offered_capacity(client, country_code_from, country_code_to, start, end):
+    contract_marketagreement_type = "A01"
+    result = client.query_offered_capacity(
+        country_code_from, country_code_to, contract_marketagreement_type, start=start, end=end, implicit=True
+    )
+    assert not result.empty
+
+
+# pandas.DataFrames
+
+@pytest.mark.parametrize(
+    "country_code, start, end, query",
+    product(COUNTRY_CODES, STARTS, ENDS, BASIC_QUERIES_DATAFRAME),
+)
+def test_basic_queries_dataframe(client, query, country_code, start, end):
+    result = getattr(client, query)(country_code, start=start, end=end)
+    assert not result.empty
+
+
+def test_query_contracted_reserve_prices(client, country_code, start, end):
+    type_marketagreement_type = "A01"
+    result = client.query_contracted_reserve_prices(
+        country_code, start=start, end=end, type_marketagreement_type=type_marketagreement_type, psr_type=None 
+    )
+    assert not result.empty
+
+
+def test_query_contracted_reserve_amount(client, country_code, start, end):
+    type_marketagreement_type = "A01"
+    result = client.query_contracted_reserve_amount(
+        country_code, start=start, end=end, type_marketagreement_type=type_marketagreement_type, psr_type=None
+    )
+    assert not result.empty
+
+
+def test_query_unavailability_transmission(client, country_code_from, country_code_to, start, end):
+    result = client.query_unavailability_transmission(
+        country_code_from, country_code_to, start=start, end=end
+    )
+    assert not result.empty
+
+
+def test_query_procured_balancing_capacity_process_type_not_allowed(client, country_code, start, end):
+    process_type = "A01"
+    with pytest.raises(ValueError):
+        client.query_procured_balancing_capacity(
+            country_code, start=start, end=end, process_type=process_type
+        )
+
+
+def test_query_procured_balancing_capacity(client, country_code, start, end):
+    process_type = "A47"
+    result = client.query_procured_balancing_capacity(
+        country_code, start=start, end=end, process_type=process_type, type_marketagreement_type=None
+    )
+    assert not result.empty
diff --git a/tests/test_raw.py b/tests/test_raw.py
new file mode 100644
index 0000000..8300036
--- /dev/null
+++ b/tests/test_raw.py
@@ -0,0 +1,191 @@
+from itertools import product
+import os
+
+from bs4 import BeautifulSoup
+from dotenv import load_dotenv
+from entsoe import EntsoeRawClient
+from entsoe.exceptions import PaginationError
+import pandas as pd
+import pytest
+
+load_dotenv()
+
+API_KEY = os.getenv("API_KEY")
+
+
+@pytest.fixture
+def client():
+    yield EntsoeRawClient(api_key=API_KEY)
+
+
+def valid_xml(s: str) -> bool:
+    try:
+        BeautifulSoup(s, "html.parser")
+        return True
+    except Exception:
+        return False
+
+
+@pytest.fixture
+def start():
+    return pd.Timestamp("20171201", tz="Europe/Brussels")
+
+
+@pytest.fixture
+def end():
+    return pd.Timestamp("20180101", tz="Europe/Brussels")
+
+
+@pytest.fixture
+def country_code():
+    return "BE"  # Belgium
+
+
+@pytest.fixture
+def country_code_from():
+    return "FR"  # France
+
+
+@pytest.fixture
+def country_code_to():
+    return "DE_LU"  # Germany-Luxembourg
+
+
+STARTS = [pd.Timestamp("20171201", tz="Europe/Brussels")]
+ENDS = [pd.Timestamp("20180101", tz="Europe/Brussels")]
+COUNTRY_CODES = ["BE"]  # Belgium
+COUNTRY_CODES_FROM = ["FR"]  # France
+COUNTRY_CODES_TO = ["DE_LU"]  # Germany-Luxembourg
+
+BASIC_QUERIES = [
+    "query_day_ahead_prices",
+    "query_net_position",
+    "query_load",
+    "query_load_forecast",
+    "query_wind_and_solar_forecast",
+    "query_generation_forecast",
+    "query_generation",
+    "query_generation_per_plant",
+    "query_installed_generation_capacity",
+    "query_installed_generation_capacity_per_unit",
+    "query_aggregate_water_reservoirs_and_hydro_storage",
+]
+
+CROSSBORDER_QUERIES = [
+    "query_crossborder_flows",
+    "query_scheduled_exchanges",
+    "query_net_transfer_capacity_dayahead",
+    "query_net_transfer_capacity_weekahead",
+    "query_net_transfer_capacity_monthahead",
+    "query_net_transfer_capacity_yearahead",
+]
+
+# XML
+
+@pytest.mark.parametrize(
+    "country_code, start, end, query",
+    product(COUNTRY_CODES, STARTS, ENDS, BASIC_QUERIES),
+)
+def test_basic_queries(client, query, country_code, start, end):
+    result = getattr(client, query)(country_code, start, end)
+    assert isinstance(result, str)
+    assert valid_xml(result)
+
+
+@pytest.mark.parametrize(
+    "country_code_from, country_code_to, start, end, query",
+    product(COUNTRY_CODES_FROM, COUNTRY_CODES_TO, STARTS, ENDS, CROSSBORDER_QUERIES),
+)
+def test_crossborder_queries(
+    client, query, country_code_from, country_code_to, start, end
+):
+    result = getattr(client, query)(country_code_from, country_code_to, start, end)
+    assert isinstance(result, str)
+    assert valid_xml(result)
+
+
+def test_query_intraday_offered_capacity(client, country_code_from, country_code_to, start, end):
+    result = client.query_intraday_offered_capacity(
+        country_code_from, country_code_to, start, end, implicit=True
+    )
+    assert isinstance(result, str)
+    assert valid_xml(result)
+
+
+def test_query_offered_capacity(client, country_code_from, country_code_to, start, end):
+    contract_marketagreement_type = "A01"
+    result = client.query_offered_capacity(
+        country_code_from, country_code_to, start, end, contract_marketagreement_type, implicit=True
+    )
+    assert isinstance(result, str)
+    assert valid_xml(result)
+
+
+def test_query_contracted_reserve_prices(client, country_code, start, end):
+    type_marketagreement_type = "A01"
+    result = client.query_contracted_reserve_prices(
+        country_code, start, end, type_marketagreement_type, psr_type=None
+    )
+    assert isinstance(result, str)
+    assert valid_xml(result)
+
+
+def test_query_contracted_reserve_amount(client, country_code, start, end):
+    type_marketagreement_type = "A01"
+    result = client.query_contracted_reserve_amount(
+        country_code, start, end, type_marketagreement_type, psr_type=None
+    )
+    assert isinstance(result, str)
+    assert valid_xml(result)
+
+
+def test_query_procured_balancing_capacity_bytearray(client, country_code, start, end):
+    process_type = "A47"
+    result = client.query_procured_balancing_capacity(
+        country_code, start, end, process_type, type_marketagreement_type=None
+    )
+    assert isinstance(result, str)
+    assert valid_xml(result)
+
+
+def test_query_procured_balancing_capacity_process_type_not_allowed(client):
+    type_marketagreement_type = "A01"
+    process_type = "A01"
+    with pytest.raises(ValueError):
+        client.query_procured_balancing_capacity(
+            country_code, start, end, process_type, type_marketagreement_type
+        )
+
+# ZIP
+
+def test_query_imbalance_prices(client, country_code, start, end):
+    result = client.query_imbalance_prices(country_code, start, end, psr_type=None)
+    assert isinstance(result, (bytes, bytearray))
+
+
+def test_query_unavailability_of_generation_units(client, country_code, start, end):
+    result = client.query_unavailability_of_generation_units(country_code, start, end, docstatus=None, periodstartupdate=None, periodendupdate=None)
+    assert isinstance(result, (bytes, bytearray))
+
+
+def test_query_unavailability_of_production_units(client, country_code, start, end):
+    result = client.query_unavailability_of_production_units(country_code, start, end, docstatus=None, periodstartupdate=None, periodendupdate=None)
+    assert isinstance(result, (bytes, bytearray))
+
+
+def test_query_unavailability_transmission(
+    client, country_code_from, country_code_to, start, end
+):
+    result = client.query_unavailability_transmission(
+        country_code_from, country_code_to, start, end, docstatus=None, periodstartupdate=None, periodendupdate=None
+    )
+    assert isinstance(result, (bytes, bytearray))
+
+
+def test_query_withdrawn_unavailability_of_generation_units(
+    client, country_code, start, end
+):
+    result = client.query_withdrawn_unavailability_of_generation_units(
+        country_code, start, end,
+    )
+    assert isinstance(result, (bytes, bytearray))